The short version: because it grows so quickly, the root system isn't damaged by harvesting and it's so plentiful -- "For a lumber harvester, the yield can be 25 times what you'd get from regular ol' trees" -- growing it is really green, but manufacturing it into useful plywood boards, for anything that the tubular stalks won't do on their own...well, not so much. It's a pretty messy, intensive process; as such, it's important to look for bamboo made with water-based, formaldehyde-free adhesives with low/no-VOC finishes, if you're looking for some grass-based interiors. All bamboo isn't as green as advertised; get down to the nitty-gritty over at ::Core77